1. Field of the Invention
The present invention is related to the area of image sensors and surveillance. More particularly, the present invention is related to CMOS sensors with high-sensitivity, and system and method for monitoring multiple targets using a single camera.
2. Description of Related Art
Surveillance is the monitoring of the behavior, activities, or other changing information, usually of people for the purpose of influencing, managing, directing, or protecting. In general, the word surveillance is applied to observation from a distance by means of electronic equipment (such as CCTV cameras), or interception of moving information (such as various traffic).
Surveillance is very useful to governments and law enforcement to maintain social control, recognize and monitor threats, and prevent or investigate dangerous activity. With the advent of sophisticated surveillance systems in place, various agencies now possess the unprecedented ability to monitor the activities of their subjects.
Traffic cameras are an innovative and extremely functional use of video surveillance technology. They are atop traffic signals and placed along busy roads, and at busy intersections of the highway. Whether they are recording traffic patterns for future study and observation or monitoring traffic and issuing tickets for moving violations, traffic cameras are an explosively popular form of video surveillance.
It is commonly seen that multiple cameras are often in place to monitor a section of road. When there are eight forward and backward lanes in a typical highway, four or eight cameras are often used, each is configured to monitor one or two lanes. Besides the installation complexity involving an overhead structure across the lanes, the cost of the cameras and the associated supporting system to control the cameras is of extremely high.
Accordingly, there is a need for traffic surveillance systems that can be installed and put into use without the associated installation complexity and costs. Further there is a need for a surveillance system capable of monitoring multiple targets using one camera or a single image sensor.
In the application of video surveillance, the characteristics of the image sensor(s) being used is very important to the entire surveillance system. An image sensor is a device that converts a scene or an optical image into an electronic signal. There are essentially two types of image sensors, charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) image sensors. In general, CCD image sensors are more expensive than CMOS image sensors because CMOS sensors are less expensive to manufacture than CCD sensors. CMOS image sensors can potentially be implemented with fewer components, use less power, and/or provide faster readout than CCD image sensors can. Thus CMOS image sensors are getting considerable attentions. Another common understanding is that CCD image sensors are more sensitive to light variations than CMOS image sensors. Thus there is a further need for techniques that can enhance the sensitivity of CMOS image sensors.